Fracture toughness characterization of austempered ductile iron produced using both conventional and two-step austempering processes

Abstract The aim of the present study is to characterize mainly fracture toughness as well as the other mechanical properties of austempered ductile iron produced using both single-step and two-step austempering processes. The effect of alloying with Ni and Mo has been investigated. Austempering heat treatment was conducted at temperatures between 260 °C and 390 °C. Plane strain fracture toughness was evaluated for each material and heat treatment condition. It was found that two-step austempering process resulted in improving the fracture toughness of the material, while maintaining reasonable levels of strength. Alloyed samples showed higher fracture toughness than un-alloyed ones.